Process for the production of amylose articles by extrusion of aqueous sodium hydroxide solution thereof into concentrated aqueous ammonium sulphate solution



United States Patent Pieter Hiemstra, Veendam, and Johannes Muetgeert, Delft, Netherlands, assignors to Coiiperatieve Verkoopen Productievereniging Van Aardappelmeel en Derivaten Avebe G.A., Veendam, Netherlands Application October 20, 1958 Serial No. 768,071

Claims priority, application Netherlands October 22, 1957 3 Claims. (Cl. 18--54) No Drawing.

The invention relates to a process for the production of articles of manufacture, such as films and fibres, from amylose.

It is known that amylose films can be made by means of casting process. Processes of such a type, whereby an amylose solution is prepared by dissolving amylose in water e.g. with the aid of a complex forming agent or in an aqueous solution of an aldehyde such as for example formaldehyde, and wherein this solution is cast on a support on which it is dried, are relatively expensive, chiefly because the drying and coagulation rates are limited, and the process is consequently rather slow.

Attempts have been made at making fibres and films from an amylose solution by extrusion into a coagulation bath, but none of the attempts that have so far been made have yielded any useful results. In some cases, as for example by extruding amylose, which had been dissolved in an aqueous sodium hydroxide solution, into an acid bath as coagulation bath, a fibre or film was obtained by gelation, but the amylose film or fibre which had coagulated in this manner was so weak as to be practically untransportable.

It has now been found that amylose dissolved in an aqueous sodium hydroxide solution, when extruded into a concentrated aqueous ammonium sulphate solution, coagulates almost instantaneously, whereby a fairly strong, very resilient film or fibre is obtained, which is eminently free supporting and therefore very transportable.

As a measure for the coagulation rate the spinning rate may serve; for the coagulation rate is so high that it is hardly measurable in itself. In applying the process according to the invention spinning rates up to about 50 metres per minute were reached, whilst with casting processes rates of not more than 4 to 5 metres per minute could be reached.

Extrusion can be done through an opening of a round or rectangular or polygonal shape so that fibres or films and the like are formed.

The concentration of the ammonium sulphate in the coagulation bath is exceedingly important. With concentrations of 30 percent by weight and lower, the spinning rate is only a few metres a minute. With a concentration of 40%, however, this rate is already about 35 rn./minute, and in a saturated aqueous solution of ammonium sulphate spinning rates of up to 50 mjrninute could be realized.

Hereby a pH value of between 7.5 and 8.0 is automatically established in the coagulation bath. In extruding a solution of amylose in aqueous sodium hydroxide the following reaction takes place in the spinnnig bath:

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By the high concentration of NH,+ ions the dissociation of the NH OH which has been formed is pushed back and the above-mentioned pH value is reached automatically.

Attempts at accelerating the process by adding an acid to the coagulation bath did not bring about the desired result. It is true that coagulation in a bath of the type where acid is added is very swift, but the film or fibre thus obtained is very weak and its transportation and further working up is very difiicult. It would seem, therefore that a high H+-ion concentration is unfavourable for obtaining a strong amylose gel in the coagulation bath.

A very suitable extrusion bath contains NH OH and more than 30 percent by weight of ammonium sulphate.

Naturally, the films and fibres obtained by coagulation, can be freed of the inorganic compounds they had taken up, by washing with a suitable solvent, in which the amylose is not soluble, as for example a mixture of water and alcohol or more generally mixtures of water and organic water soluble substances, and subsequently dried.

Amylose films have the advantage of consisting of easily digestible material, and are therefore eminently suitable for packing food, as these films can be consumed with the packed product.

Example 224 g. of air-dry commercial amylose in powder form (moisture content 12% by weight) was dispersed in 1070 g. of air-free distilled water at a temperature of 20 C. whilst stirring vigorously. To the viscous mass thus obtained a solution of 50 g. of sodium hydroxide in 156 g. of air-free distilled water was added whilst stirring vigorously. After three more hours of stirring a solution was obtained, in which no undissolved amylose had been left.

The solution was subsequently filtered over a vacuum filter through filtering cloth with a high mesh-number. This solution was kept in vacuum for 24 hours, in order to remove dissolved gases if any.

The solution thus obtained was optically void and contained 13.2% by weight of amylose and 3.3% by weight of NaOH, and had a viscosity of 10002000 centipoises.

The solution was extruded from a spinnerette of platinum rhodium with 30 apertures, each of which having a diameter of 0.100 mm., into a spinning bath of 30 C., consisting of a solution of ammonium sulphate in distilled water, which solution contained 43-44% by weight of (NH SO The fibres which were formed were led through the bath for about 2 seconds and subsequently wound on a bobbin (at a rate of about 45 m./ minute) The closing of the spinning solution was 3.8 cm. a minute; the filaments obtained had, after washing and drying, a denier of 3.3.

If, instead of a spinnerette with round apertures, a slot having a width of 0.1 mm. is used for extruding the spinning solution, an amylose film can be produced at approximately the same rate.

Impurities may influence the properties of the fibres and films obtained to a large extent. In order to obtain the greatest possible strength, ammonium sulphate should be removed as completely as possible. This can be done by thorough washing.

It proved to be possible, however, to replace part of the amylose by amylopectin without exerting a distinctly unfavourable influence on the properties of the films.

What we claim is:

1. In a process for the production of articles of manufacture such as fibres and films from amylose, the step of dissolving amylose in an aqueous sodium hydroxide solution and extruding this solution into a concentrated aqueous ammonium sulphate'solution.

2. The process according to claim 1, wherein the coagulation bath, in addition to more than 30% sy Weight of '(NH )2SO also contains 'NH OH.

3. The process according to claim 1 wherein the coagulation bath has a pH value of 7.5-8.

References Cited in the file of this patent UNITED STATES PATENTS Levey Nov. 15, 1938 Reid et a1. Jan. 31, 1950 Horsak Oct. 9, 1951 Wolfi et a1 Sept. 2, 1952 Muetgurt et al Feb. 11, 1958 Wimmer Sept. 23, .1958 

1. IN A PROCESS FOR THE PRODUCTION OF ARTICLES OF MANUFACTURE SUCH AS FIBRES AND FILMS FROM AMYLOSE, THE STEP OF DISSOLVING AMYLOSE IN AN AQUEOUS SODIUM HYDROXIDE SOLUTION AND EXTRUDING THIS SOLUTION INTO A CONCENTRATED AQUEOUS AMMONIUM SULPHATE SOLUTION. 